1. Field of the Invention
The invention relates generally to modified thermoplastic rubber formulations useful as coatings in wet use environments and particularly to such coatings useful as high wet friction coatings on surfboards, bathtubs, shower stalls, boat decking and the like.
2. Description of the Prior Art
Literally hundreds of use environments exist wherein safety or other considerations are improved by the availability of a surface coating which provides improved friction when the surface is wetted. A typical application is for the deck of a surfboard and on surfaces of similar equipment including wind surfing watercraft, bodyboards, and certain surfaces of jet skiis including the rubber pads which are normally intended to contact a user's feet. Other sporting equipment such as gloves, diving boards, hand rails and ladders used around swimming pools as well as boat decks and docks would have improved performance by the availability of an anti-slip coating which is effective when wetted by water and particularly over a relatively wide range of temperatures. Other surfaces which typically become slippery when wetted with water include shoe soles, surgical gloves, automobile tires, bathtub surfaces and shower stall surfaces, particularly shower stall floors, bathroom floors, conveyor belts handling wet products, there being a substantial need over a very wide range of applications for coatings which exhibit substantial traction or friction when said surfaces are wetted by water.
In the prior art, it has generally been necessary to provide enhanced friction in coatings on surfaces as described above by the provision in such a coating of a filler material such a silicon dioxide, high-strength glass microspheres, or other filler materials which provide increased surface roughness and therefore increase the overall anti-slip characteristics of such coatings. However, the prior art coatings having at least some degree of anti-slip properties and which include fillers and materials for increasing the roughness of the surface coating are inadequate in many situations due to the fact that the abrasiveness imparted by the fillers is unacceptable when such coatings must contact human skin. For example, U.S. Pat. No. 4,745,139 to Haasl et al provides surface coating formulations which are intended to improve traction on a surface which is frequently contacted with water, the disclosed coatings being provided with fillers including particulate colloidal or powdered silicon dioxide and/or glass microspheres. When a coating according to Haasl et al is applied to the deck of a surfboard, for example, the roughened coating irritates and abrades the skin of a user, especially when a user lies prone on the surfboard as when paddling the board out to catch a wave. The present coating formulations provide increased frictional and anti-slip surface characteristics without incorporation of fillers to roughen the surfaces of the coatings. The present coating formulations thus are useful in at least those applications delineated by Haasl et al in U.S. Pat. No. 4,745,139 and further provide the advantage of being unabrasive to the skin of a user.
Haasl et al, in U.S. Pat. No. 4,745,139, and Haasl in U.S. Pat. No. 4,536,454, provide thermoplastic rubber formulations which are compounded with styrene/ethylene/butylene/styrene block copolymers. The thermoplastic rubber formulations provided in these patents derive increased anti-slip characteristics by virtue of fillers included in the thermoplastic rubber formulations and which fillers act to roughen the surfaces of coatings formed from said formulations. The formulations of Haasl and Haasl et al do not provide relatively soft surfaces for their coatings which are non-abrasive to human skin and which can contact human skin with a high degree of comfort. The present invention improves the anti-slip coating formulations of Haasl and Haasl et al at least by the provision of petrolatum in thermoplastic rubber formulations, this additional material providing in thermoplastic rubber formulations a surface coating having high anti-slip properties when wet and which also is compatible with contact with the skin of a user of the coating, the coating formulations also adhering reliably to surfaces such as the decks of surfboards, etc. and which also have high tensile strengths.
Dotson et al, in U.S. Pat. No. 4,990,184, provides coating compositions containing petrolatum and polymerizable materials used to form corrosion resistant coatings. However, Dotson et al do not provide coatings which have anti-slip properties when wet. The polymers used by Dotson et al include linear polyethylene polymers having terminal carboxylic acid groups, polybutenes and amorphous polypropylenes. Accordingly, the coatings of Dotson et al, even though including a petrolatum material, would not lead a person of ordinary skill in the art to the compounding of thermoplastic rubbers with petrolatum to provide a film or coating having increased traction when wet. The present invention thus provides a substantial advance in the art relative to the compounding of thermoplastic rubbers with petrolatum to provide a surface coating for the surface of a surfboard or the like whereby the surface coating is adherent to the surface of the surfboard and which provides traction or friction improvement when wet and which is also agreeable to skin touch.